The ovary secretes both steroid hormones and a spectrum of protein hormones that are of great importance to the control of reproductive function. However, little is presently known of the cellular and molecular pathways that regulate release of ovarian protein hormones. In these proposed studies, a more complete understanding of one such hormone, the protein hormone relaxin, will be attempted by characterizing the secretagogues and intracellular signalling pathways that subserve secretory function, together with an analysis of structure-function relationships. These objectives will be met by use of a reverse hemolytic plaque assay. This assay is based on antibody-directed, complement- mediated lysis of erythrocytes adjacent to hormone secretors, thus enabling the microscopic visualization of hormone release from individual luteal cells in culture. The primary objectives of the proposed studies are: (a) to evaluate the relative importance of, and differential response to, stimulatory (prostaglandins) and inhibitory (LH, auto-suppression) secretagogues for relaxin release; (b) to characterize the influence, interactions and relative importance of, and differential response to, second messenger pathways such as cyclic nucleotides, calcium mobilization, protein kinase C activation and arachidonic acid metabolites, and to determine if luteal cells function as excitable cells; and (c) to determine the secretory characteristics of luteal cells that contain relaxin but do not release relaxin ("silent" cells"). To accomplish these goals, the secretory characteristics of single hormone-secretors will be monitored, in combination (where appropriate) with immunocytochemical techniques. It is anticipated that meaningful information will be derived concerning the identity, importance and interactions of cellular and molecular mechanisms that subserve ovarian hormone release. Moreover, new insights into the enigma of non-releasing secretory cells will be gained. This knowledge can eventually be used not only to identify the causes of (and developing treatments for) ovarian pathologies, but also to identify new strategies for regulating human ovarian function.